Data storage devices store digitally encoded information on a data storage medium, such as a disc. A head is used to read and/or write information to the disc or storage medium. The head includes a transducer element, such as a writer and/or reader which is fabricated on or coupled to a slider body to read and/or write information to the disc.
Typically, the head flies over the disc surface via pressurization of an air bearing surface or surfaces of the slider body. In particular, during operation, rotation of the disc creates an airflow along air bearing surfaces of the slider so that the slider floats above the disc surface for read or write operations. The head is positioned relative to data tracks on the disc surface via a head actuator. The head is coupled to the actuator via a suspension assembly. The suspension assembly includes a load beam which supplies a load force to the slider body which counteracts the lifting force of the air-bearing surface to provide a fly height of the slider body relative to the disc surface.
Manufacturing processes and tolerances introduce a waviness or asperities to the disc surface. Disc waviness or variations can introduce pressure disturbances or gradients along the air-bearing surface. Typically, air-bearing surfaces compensate for different pressure gradients to provide a relatively stable fly height for the slider body or head. As form factor size decreases and drive storage density increases, fly heights for the data heads relative to the disc surface are decreasing. With the lower fly heights, it is more difficult for the air bearing surface to compensate for disc waviness or other topographical irregularities to prevent non-contact or contact-induced head-media spacing instabilities detrimental to disc drive performance.
Sensors, for example glide head sensors, are used to provide feedback of head-disc contact or interference. Prior sensors detect or monitor excitation of slider structural modes. Excitation of the slider structural modes typically requires high levels of interference between the head and the disc. As flying heights are reduced to enable increasing drive storage densities, non-contact instabilities or low level interference become more significant. The present invention provides solutions to these and other problems, and offer other advantages over the prior art.